The accumulation of dead/rotting foliage forms a thick ground cover which, over time, eliminates the growth and establishment of other vegetation (Ruskin, 1983). When it forms dense thickets along waterways it reduces water flow and can contribute to flooding (Hill et al., 2000) and streambank erosion. It has a significant impact on water runoff, and because it fixes nitrogen, it alters soil nutrient cycling. Its pollen is reported to be allergenic.